Copy and pasting with CTRL + C and CTRL + V from one scene to another isn't working!
This phenomena could be caused by having to less RAM memory present on your computer,(since all data from one blender project needs to be  in RAM memory, before it can be   into the 2nd Blender again.

Here are a few solutions:
1 - Close down every other applications you do not use at that moment and then do the copy-and-paste operation again. See how that works.

2 - Copy and Paste object by object instead of everything at once

3 - Export all needed objects (to hard-disk) and then import them again from the 2nd blender application

4 - If all fails, re-create the object in the 2nd scene.